Temperature measurement method and device based on photoelastic modulation magneto-optic Kerr optical system

Abstract

The application discloses a kind of temperature measurement method and device based on photoelastic modulation magneto-optical Kerr optical system, belong to magneto-optical detection and temperature measurement technical field, comprising: S 1, the optical axis azimuth angle of the polarizer and the photoelastic modulator is adjusted, so that the detection light intensity of the photoelectric detector only has direct current component;And the optical axis azimuth angle α of the polarizer is set to be less than 45°, and under the azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition;S2, according to the detection light intensity, the direct current amplitude, the first harmonic amplitude and the second harmonic amplitude of light intensity at photoelastic modulation frequency are obtained by Fourier transform;S3, the magneto-optical signal of magnetic nanometer film sample is calculated;S4, the temperature of the magnetic nanometer film sample is changed, and the numerical relationship between the magneto-optical signal MO (T) and temperature T is calibrated.The application can directly measure temperature based on photoelastic modulation magneto-optical Kerr optical system, and the resolution of temperature measurement on the surface of sample can reach mK level.

Description

Technical Field

[0001] This invention belongs to the field of magneto-optical detection and temperature measurement technology, and more specifically, relates to a temperature measurement method and device based on a photoelastic modulation magneto-optical Kerr optical system. Background Technology

[0002] Real-time temperature monitoring is of great significance for micro- and nano-manufacturing and temperature monitoring for chip reliability. However, transient heat exchange processes at the micro- and nano-scale involve rapid temperature changes and short durations due to their small specific heat capacity. Therefore, high temporal resolution and high sensitivity are required for temperature measurement. Optical thermometry can achieve non-contact temperature measurement and transmit temperature information at the speed of light, significantly improving the temporal resolution of temperature measurements.

[0003] In magnetized nanofilms, the magneto-optical Kerr signal changes with temperature, thus temperature information can be obtained by measuring the magneto-optical Kerr signal. Since the temperature-dependent magneto-optical Kerr signal of nanofilms is extremely weak, mostly on the order of mrad or even urad, a photoelastic modulator with high-frequency polarization modulation is typically used to simultaneously improve the real-time performance and sensitivity of temperature measurements. In a photoelastic modulated magneto-optical Kerr measurement system, the Kerr signal is modulated onto the harmonics of the photoelastic modulation frequency, and the ratio of AC to DC harmonics can be used to separate the temperature-dependent Kerr signal.

[0004] In existing photoelastic modulated magneto-optical Kerr measurement systems, the optimal configuration of the optical system is typically set to an analyzer azimuth angle of 45°, maximizing the amplitude of each harmonic change in the Kerr signal. However, in temperature measurement, this configuration with the highest harmonic amplitude does not guarantee the highest signal-to-noise ratio of the temperature sensing signal, resulting in poor temperature sensitivity in traditional configurations. Summary of the Invention

[0005] To address the shortcomings and improvement needs of existing technologies, this invention provides a temperature measurement method and device based on a photoelastic modulation magneto-optical Kerr optical system, with the aim of improving temperature detection sensitivity.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a temperature measurement method based on a photoelastic modulation magneto-optical Kerr optical system is provided. The photoelastic modulation magneto-optical Kerr optical system includes a polarizer, a photoelastic modulator, an analyzer, and a photodetector. The temperature measurement method includes:

[0007] S 1. Adjust the optical axis azimuth angle of the polarizer and the photoelastic modulator so that the detection light intensity of the photodetector has only a DC component; and set the optical axis azimuth angle α of the analyzer to be less than 45°, and under the azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition;

[0008] S2. Based on the detected light intensity, obtain the DC amplitude, first harmonic amplitude, and second harmonic amplitude of the light intensity at the photoelastic modulation frequency through Fourier transform;

[0009] S3. Calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample, wherein the magneto-optical signal MO(T) is the ratio of the first harmonic amplitude and the second harmonic amplitude to the DC amplitude, respectively;

[0010] S4. Change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T.

[0011] Furthermore, the optical axis azimuth angle α of the analyzer is such that the intensity of the probe light is greater than the minimum value of the data acquisition quantization error.

[0012] Furthermore, setting the optical axis azimuth angle α of the analyzer to a value that makes the intensity of the probe light greater than the minimum value of the data acquisition quantization error includes:

[0013] Rotate the optical axis of the analyzer so that the intensity of the probe light gradually decreases from its maximum value to close to its minimum value. When the intensity of the probe light is greater than the data acquisition quantization error, fix the optical axis of the analyzer to obtain the required optical axis azimuth angle α.

[0014] Furthermore, the DC amplitude V DC First harmonic amplitude V f Second harmonic amplitude V 2f They are respectively:

[0015]

[0016] V 1f =I0|r ss |K 1f 2J1(π)sin2αε k (T)

[0017] V 2f =I0|r ss |K 2f 2J2(π)sin2αθ k (T)

[0018] Among them, K DC K 1f and K 2f These are the amplification factors of the photodetector at DC, first harmonic, and second harmonic frequencies, respectively; J i (π) is the Bessel function of cosδ and sinδ at the i-th harmonic, where i takes values ​​of 0, 1, 2, and δ is the periodic delay generated by the photoelastic modulator; θ k ε kLet represent the real part of the magneto-optical Kerr angle, the Kerr rotation angle, and the imaginary part, the ellipticity, respectively; I0 is the original intensity of the incident light; r ss This represents the Jones matrix coefficients of the sample.

[0019] Furthermore, the magneto-optical signal MO(T) is:

[0020]

[0021]

[0022] Among them, MO f (T) represents the amplitude of the first harmonic V. f With the DC amplitude V DC The ratio of MO; 2f (T) represents the amplitude of the second harmonic V. 2f With the DC amplitude V DC The ratio of .

[0023] Furthermore, when the optical axis azimuth angles of the polarizer and the photoelastic modulator are adjusted to 90° and 0° respectively, the detection light intensity of the photodetector only has a DC component.

[0024] Furthermore, it also includes:

[0025] S5. Based on the numerical relationship between the magneto-optical signal MO(T) calibrated in S4 and the temperature T, calculate the actual temperature corresponding to the currently measured magneto-optical signal using a fitting method or a table lookup method.

[0026] According to a third aspect of the present invention, a temperature measuring device based on a photoelastic modulation magneto-optical Kerr optical system is provided for performing the temperature measuring method according to any one of the first aspects, the temperature measuring device comprising:

[0027] The optimization configuration module is used to adjust the optical axis azimuth angle of the polarizer and the photoelastic modulator so that the detection light intensity of the photodetector has only a DC component; and to set the optical axis azimuth angle α of the analyzer to be less than 45°, and at the azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition;

[0028] The harmonic amplitude calculation module is used to obtain the DC amplitude, first harmonic amplitude, and second harmonic amplitude of the light intensity at the photoelastic modulation frequency by Fourier transform based on the detected light intensity.

[0029] A magneto-optical signal calculation module is used to calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample, wherein the magneto-optical signal MO(T) is the ratio of the first harmonic amplitude and the second harmonic amplitude to the DC amplitude, respectively;

[0030] The temperature calibration module is used to change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T.

[0031] Furthermore, the modulation frequency of the photoelastic modulator is not less than 50 kHz.

[0032] According to a third aspect of the invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the temperature measurement method as described in any of the first aspects.

[0033] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0034] (1) The method of this invention uses the harmonic ratio as the temperature sensing signal. When the detected light intensity has only a DC component, the optical axis azimuth angle α of the analyzer is configured to be less than 45°, and the detected light intensity I is greater than the quantization error of the data acquisition. This avoids additional sensitivity loss caused by quantization noise, while improving the signal gain of the magneto-optical signal, increasing the signal-to-noise ratio of the harmonic ratio, and thus improving the temperature measurement sensitivity. Furthermore, this invention directly achieves high-sensitivity measurement of temperature T based on a photoelastic modulation magneto-optical Kerr optical system.

[0035] (2) Preferably, when the optical axis azimuth angle of the analyzer is such that the intensity of the probe light is greater than the minimum value of the data acquisition quantization error, the signal gain of the magneto-optical signal MO is the largest, and the corresponding temperature measurement sensitivity is the highest.

[0036] (3) The present invention uses the AC / DC harmonic ratio as the magneto-optical signal for temperature sensing, which can avoid the influence of the original light intensity fluctuation of the incident light on the single harmonic amplitude and improve the accuracy of temperature measurement.

[0037] (4) The magneto-optical temperature measurement method of the present invention is a non-contact, non-invasive measurement method; it can be used in different temperature ranges of different samples, and has the advantage of a wide temperature measurement range.

[0038] (5) The magneto-optical temperature measurement method of the present invention has the advantages of optical measurement. The photoelastic modulator modulates the light at a high frequency of at least 50 kHz, which makes the measurement speed easily reach the microsecond level and has high time resolution. Attached Figure Description

[0039] Figure 1 This is a flowchart of the temperature measurement method based on the photoelastic modulation magneto-optical Kerr optical system of the present invention.

[0040] Figure 2 This is a diagram of a photoelastic modulation magneto-optical Kerr optical system in an embodiment of the present invention.

[0041] Figure 3This is a simulation diagram of the magneto-optical signal gain of the analyzer under different configurations in this embodiment of the invention.

[0042] Figure 4 The simulation results of the signal gain of the magneto-optical signal and the probe optical signal under different analyzer optical axis azimuth angles are shown in the embodiments of the present invention.

[0043] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0044] 1-Laser source; 2-Polarizer; 3-Beam splitter prism; 4-Photoelastic modulator; 5-Analyzer; 6-Convex lens; 7-Filter; 8-Photodetector; 9-Acquisition card; 10-Host computer. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] like Figure 1 , Figure 2 As shown, the present invention provides a temperature measurement method based on a photoelastic modulation magneto-optical Kerr optical system. In this embodiment, the photoelastic modulation magneto-optical Kerr optical system includes: a laser source 1, a polarizer 2, a beam splitter 3, a photoelastic modulator 4, an analyzer 5, a convex lens 6, a photodetector 8, a data acquisition module, and a central processing module.

[0047] The light propagation path is as follows: the laser beam emitted by the laser source 1 passes perpendicularly through the center of the polarizer 2 and becomes linearly polarized light; the linearly polarized light is irradiated onto the surface of the magnetic nanofilm sample by the beam splitter 3 and reflected. Simultaneously, under the influence of magnetic field excitation and temperature change, the magnetic nanofilm sample changes the polarization state of the reflected light, generating a magneto-optical Kerr signal; the reflected light carrying the magneto-optical Kerr signal is subjected to high-frequency modulation of the polarization state by the photoelastic modulator 4 and then passes through the analyzer 5 to determine the current polarization state of the light, so as to facilitate subsequent separation of the magneto-optical Kerr signal; the probe light after passing through the analyzer 5 is focused into the photosensitive area of ​​the photodetector 8 by the convex lens 6, and the probe light intensity is converted into a voltage signal; the voltage signal is acquired by the data acquisition module, converted into a voltage signal, and then converted into a digital signal and sent to the central processing module for subsequent processing. In this embodiment of the invention, the data acquisition module includes a high-speed acquisition card 9. To satisfy Shannon's sampling law, the sampling rate of the acquisition card is at least twice the photoelastic modulation frequency; the central processing module includes a host computer 10 capable of real-time communication with the acquisition card and software and programs for data processing and calculation.

[0048] The filter 7 is also included between the convex lens 6 and the photodetector 8. The peak transmittance wavelength of the filter 7 is the wavelength of the laser beam emitted by the laser source 1.

[0049] In the initial installation of the aforementioned photoelastic modulation magneto-optical Kerr optical system, the light beam is arranged to pass perpendicularly through or be reflected perpendicularly into each component. Specifically, the laser output light is adjusted to pass perpendicularly through the center of the polarizer, and then the light reflected from the surface of the thin film sample passes perpendicularly through the photoelastic modulator, analyzer, convex lens, and filter before all of it irradiating the photosensitive area of ​​the photodetector. The magnetic field excitation direction is a poloidal static magnetic field perpendicular to the surface of the magnetic nanofilm sample. The magnetic field excitation module includes, but is not limited to, permanent magnets, electromagnets, and other tools capable of generating static magnetic fields.

[0050] In this embodiment of the invention, the temperature measurement method based on a photoelastic modulated magneto-optical Kerr optical system mainly includes the following steps:

[0051] S 1. Adjust the optical axis azimuth angle of polarizer 2 and photoelastic modulator 4 so that the detection light intensity of photodetector 8 has only DC component; and set the optical axis azimuth angle α of analyzer 5 to be less than 45°, and under this azimuth angle α, the detection light intensity I is greater than the quantization error of data acquisition; in this embodiment of the invention, the quantization error of data acquisition is the quantization noise threshold of data acquisition module.

[0052] S2. Based on the detected light intensity of photodetector 8, the DC amplitude V of the light intensity at the photoelastic modulation frequency is obtained through Fourier transform. DC First harmonic amplitude V f Second harmonic amplitude V 2f ;

[0053] S3. Calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample, where the magneto-optical signal MO(T) is defined as the AC / DC harmonic ratio of the voltage signal after the probe light intensity conversion, i.e., the first harmonic amplitude V. f and the amplitude of the second harmonic V 2f respectively with DC amplitude V DC The ratio;

[0054] S4. Change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T.

[0055] Specifically, in S1, when the optical axis azimuth angles of polarizer 2 and photoelastic modulator 4 are adjusted to 90° and 0° respectively, the photodetector 8 detects only a DC component in the optical signal. The process of adjusting the optical axis azimuth angles of polarizer 2 and photoelastic modulator 4 includes:

[0056] With the optical axis azimuth angle of the fixed polarizer 2 at 90°, observe the intensity of the detected light from the photodetector and adjust the optical axis azimuth angle of the photoelastic modulator 4 until the intensity of the detected light from the photodetector 8 has only a DC component. At this time, the optical axis azimuth angle of the photoelastic modulator 4 is 0°, and regardless of the direction of the optical axis of the analyzer 5, all harmonics of the detected light intensity are at their minimum values.

[0057] Specifically, after the optical axis azimuth angles of polarizer 2 and photoelastic modulator 4 are adjusted, the optical axis azimuth angles of polarizer 2 and photoelastic modulator 4 are fixed, and the optical axis of analyzer 5 is rotated so that the detection light intensity of photodetector 8 gradually decreases from the maximum value to close to the minimum value. The minimum detection light intensity corresponds to the optical axis azimuth angle of analyzer 5 being 0°. In this embodiment of the invention, when the detection light intensity is close to the extinction position of the minimum value and the detection light intensity is slightly greater than the quantization error of data acquisition, the optical axis azimuth angle of analyzer is fixed.

[0058] In this embodiment of the invention, the propagation path of the temperature signal is as follows: temperature affects the magnetization intensity, which in turn changes the magneto-optical Kerr signal, thereby changing the intensity of the probe light, and finally converting it into an electrical signal through a photodetector. The relationship between the magneto-optical signal MO and the temperature T, MO(T), is jointly determined by the magnetocaloric effect and the magneto-optical Kerr effect.

[0059] The magnetocaloric effect refers to the relationship between the magnetization M of a ferromagnetic material and its temperature T. Magnetization changes with temperature, generally conforming to Curie-Weiss's law; below the Curie temperature of the material, magnetization decreases with increasing temperature. The specific numerical relationship between magnetization and temperature varies depending on the element and composition, and can be measured beforehand using a superconducting magnetometer.

[0060] The magneto-optical Kerr effect refers to the relationship between the complex magneto-optical Kerr angle θ and the magnetization M. θ can be decomposed into the real part Kerr rotation angle θ. k and the imaginary part of ellipticity ε k θ of the thin film sample k and ε k Both are linearly related to magnetization. The relationship between the complex magneto-optical Kerr angle θ and magnetization can be described as:

[0061] θ=θ k +iε k

[0062] Specifically, in S2, the electric field E of the photodetector 8 is the detection light intensity. out The Jones matrix equation is:

[0063] E out =A·R(α)·R(-m)·M·R(m)·S·R(-p)·P·E in

[0064] Among them, Ein and E out These are the Jones vectors of the electric fields of the incident light emitted by the laser source and the probe light of the photodetector, respectively; A, S, M, and P are the Jones matrices of the analyzer, sample, photoelastic modulator, and polarizer, respectively; p, m, and α are the optical axis azimuth angles of the polarizer, photoelastic modulator, and analyzer, respectively; R(a) is a rotation coordinate matrix with angle α, i.e., R(-p), R(α), R(m), and R(-m) represent rotation coordinate matrices with angles -p, α, m, and -m, respectively. In this embodiment of the invention,

[0065] In the formula, δ represents the periodic delay generated by the photoelastic modulator with f as the modulation angular frequency and β as the maximum amplitude, δ = βsin(2πft). The off-diagonal elements in the sample Jones matrix determine the complex Kerr angle. Where, r ps r sp r ss r pp Let represent the Jones matrix coefficients of the sample, which are related to the magneto-optical Kerr signal. Taking the polarizer azimuth angle p = 90° and the photoelastic modulator azimuth angle m = 0°, the time-domain expression for the probe intensity I can be obtained as follows:

[0066]

[0067] It can be simplified to:

[0068]

[0069] Where I0 is the original intensity of the incident light |E in | 2 where n is the harmonic order. It is the phase of each harmonic, V nf These are the amplitudes of each harmonic, which can be obtained using digital phase-sensitive detection technology.

[0070] Therefore, the DC amplitude V of the probe light intensity at the photoelastic modulation frequency is... DC First harmonic amplitude V f Second harmonic amplitude V 2f They are respectively:

[0071]

[0072] V 1f =I0|r ss |K 1f 2J1(δ)sin2αε k (T)

[0073] V 2f =I0|rss |K 2f 2J2(δ)sin2αθ k (T)

[0074] Among them, K DC K 1f and K 2f These represent the amplification factors of the photodetector at different frequencies: DC, first harmonic, and second harmonic. i (δ) is the Bessel function of cosδ and sinδ at the i-th harmonic, where i takes the values ​​0, 1, and 2.

[0075] In this embodiment of the invention, when the modulation amplitude β is 2.405 rad, J0(δ) = 0, which can effectively eliminate the change of the Kerr signal in the DC component of the light intensity and simplify the calculation.

[0076] In S3, in this embodiment of the invention, the AC / DC harmonic ratio is used as the magneto-optical signal for temperature sensing, which can avoid the influence of the original light intensity fluctuation of the incident light with a single harmonic amplitude and improve the accuracy of temperature measurement.

[0077] Specifically, the amplitudes of the first and second harmonics are divided by the DC amplitude to obtain the first harmonic ratio MO. f The ratio of the second harmonic to the second harmonic MO 2f In other words, there are two magneto-optical signals. Since the Kerr angle is typically on the order of mrad or even urad, therefore... Negligible, the magneto-optical signal MO(T) of the magnetic nanofilm sample can be obtained as follows:

[0078]

[0079]

[0080] Among them, the magnification factor and the Bessel function are temperature-independent fixed values; therefore, MO f and MO 2f These two selectable harmonic ratios, collectively referred to as the magneto-optical signal MO(T), are both single-valued functions of temperature, enabling temperature measurement. In practical applications, based on the different magneto-optical Kerr angles θ corresponding to different materials, the magneto-optical signal MO(T) with higher temperature sensitivity is selected.

[0081] In this embodiment of the invention, the signal gain of the magneto-optical signal MO(T) depends on the azimuth angle α of the analyzer. In the case where α is between 90° and 0°, as α approaches the extinction position of 0°, the intensity of the probe light decreases, and the corresponding gain of the magneto-optical signal increases significantly, far exceeding the 45° configuration of existing photoelastic modulation magneto-optical Kerr systems. The relationship between the signal gain of the magneto-optical signal MO and the analyzer azimuth angle α is as follows: Figure 3 As shown.

[0082] It can be seen that when the analyzer azimuth angle α = 45°, the signal gain is 2; when the analyzer azimuth angle α is less than 45°, the signal gain of the magneto-optical signal MO increases as α decreases; in this embodiment of the invention, when α = 1°, the signal gain increases to 115, which is 57.5 times that when α = 45°, and the signal gain is greatly improved, thereby improving the temperature measurement sensitivity.

[0083] Based on this, the optimal polarizer optical axis azimuth angle α can be configured near the 0° extinction position, that is, the polarizer optical axis azimuth angle α is configured to the minimum value that reduces the probe light intensity to above the data acquisition quantization error, which can avoid additional sensitivity loss caused by quantization noise. At this time, the signal gain of the magneto-optical signal MO is the largest, and the corresponding temperature measurement sensitivity is the highest.

[0084] Specifically, in step S4, the temperature of the magnetic nanofilm sample is changed, and the real-time temperature and corresponding magneto-optical signal are recorded to calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature. In this embodiment of the invention, a heating element attached to the back of the magnetic nanofilm sample is used to change the temperature of the magnetic nanofilm sample; a thermometer placed on the magnetic nanofilm sample is used to measure the real-time temperature.

[0085] Furthermore, the method of the present invention also includes:

[0086] S5. Based on the numerical relationship between the magneto-optical signal MO(T) calibrated in S4 and the temperature T, use spline interpolation fitting, polynomial fitting, or other fitting methods, or look up a table to calculate the actual temperature corresponding to the currently measured magneto-optical signal.

[0087] like Figure 4 As shown in the embodiments of the present invention, simulation results of the signal gains of the magneto-optical signal and the probe optical signal under different analyzer azimuth angles α are obtained when the optical axis azimuth angles of the polarizer and the photoelastic modulator are fixed at 90° and 0°, respectively. It can be seen that when the analyzer optical axis azimuth angle α is the traditional configuration of 45°, the temperature sensitivity is 0.7K. When the analyzer optical axis azimuth angle α is less than 45°, measurements were taken at three different configurations α: 2°, 4°, and 6°. As α decreases, the temperature sensitivity increases, and when α = 2°, the temperature sensitivity is better than 0.02K. That is, the method of the present invention can achieve a resolution of mK for temperature measurement of the sample surface.

[0088] According to another aspect of the present invention, a temperature measuring device based on a photoelastic modulation magneto-optical Kerr optical system is provided, wherein the specific structure of the photoelastic modulation magneto-optical Kerr optical system is as described in the above embodiment, and the device includes:

[0089] The optimization configuration module is used to adjust the optical axis azimuth angle of polarizer 2 and photoelastic modulator 4 so that the detection light intensity of photodetector 8 has only DC component; and to set the optical axis azimuth angle α of analyzer 5 to be less than 45°, and at this azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition.

[0090] The harmonic amplitude calculation module is used to obtain the DC amplitude V of the light intensity at the photoelastic modulation frequency by performing a Fourier transform based on the light intensity detected by the photodetector 8. DC First harmonic amplitude V f Second harmonic amplitude V 2f In this embodiment of the invention, the harmonic amplitude calculation module is mounted on the central processing module of the photoelastic modulation magneto-optical Kerr optical system.

[0091] A magneto-optical signal calculation module is used to calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample. In this embodiment of the invention, the magneto-optical signal calculation module is mounted on the central processing module of the photoelastic modulated magneto-optical Kerr optical system.

[0092] The temperature calibration module is used to change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T. In this embodiment of the invention, the temperature calibration module is mounted on the central processing module of the photoelastic modulated magneto-optical Kerr optical system.

[0093] Each of the above modules is used to implement the steps of the temperature measurement method based on the photoelastic modulation magneto-optical Kerr optical system in the above embodiments.

[0094] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the temperature measurement method based on a photoelastic modulation magneto-optical Kerr optical system as described in the above embodiments.

[0095] The method of this invention uses the harmonic ratio as the temperature sensing signal. When the detected light intensity has only a DC component, the optical axis azimuth angle α of the analyzer is configured to be less than 45°, and the detected light intensity I is made greater than the quantization error of data acquisition. This avoids additional sensitivity loss caused by quantization noise while improving the signal gain of the magneto-optical signal, thus improving the signal-to-noise ratio of the harmonic ratio and consequently improving the temperature measurement sensitivity. Furthermore, this invention directly achieves high-sensitivity measurement of temperature T based on a photoelastic modulation magneto-optical Kerr optical system.

[0096] The magneto-optical temperature measurement method of the present invention measures the magneto-optical signal of the magnetic nanofilm after placing the magnetic nanofilm sample in the area to be measured, and establishes a relationship model between the magneto-optical signal and temperature, thereby obtaining the real-time temperature of the area to be measured.

[0097] The magneto-optical temperature measurement method of the present invention is a non-contact, non-invasive measurement method, and the light used is not limited to infrared light, but can also be visible light. It can be selected according to different measurement scenarios and can perform non-invasive temperature measurement in different special environments.

[0098] The magneto-optical temperature measurement method of the present invention has the advantages of optical measurement. The photoelastic modulator modulates the light at a high frequency of at least 50 kHz, which makes the measurement speed easily reach the microsecond level and has high time resolution.

[0099] The magneto-optical temperature measurement method of the present invention can be used within the temperature range that the sample can withstand. Different magnetic nanofilm materials can be selected according to the different temperature ranges to be measured. Theoretically, the upper limit of the temperature measurement of the present invention is the Curie temperature of the selected magnetic nanofilm, which has the advantage of a wide temperature measurement range.

[0100] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature measurement method based on a photoelastic modulation magneto-optical Kerr optical system, wherein the photoelastic modulation magneto-optical Kerr optical system comprises a polarizer, a photoelastic modulator, an analyzer, and a photodetector, characterized in that, The temperature measurement method includes: S 1. Adjust the optical axis azimuth angle of the polarizer and the photoelastic modulator so that the detection light intensity of the photodetector has only a DC component; and set the optical axis azimuth angle α of the analyzer to be less than 45°, and under the azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition; S2. Based on the detected light intensity, obtain the DC amplitude, first harmonic amplitude, and second harmonic amplitude of the light intensity at the photoelastic modulation frequency through Fourier transform; S3. Calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample, wherein the magneto-optical signal MO(T) is the ratio of the first harmonic amplitude and the second harmonic amplitude to the DC amplitude, respectively; S4. Change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T.

2. The temperature measurement method according to claim 1, characterized in that, The optical axis azimuth angle α of the analyzer is such that the intensity of the probe light is greater than the minimum value of the data acquisition quantization error.

3. The temperature measurement method according to claim 2, characterized in that, Setting the optical axis azimuth angle α of the analyzer to ensure that the intensity of the probe light is greater than the minimum value of the data acquisition quantization error includes: Rotate the optical axis of the analyzer so that the intensity of the probe light gradually decreases from its maximum value to close to its minimum value. When the intensity of the probe light is greater than the data acquisition quantization error, fix the optical axis of the analyzer to obtain the required optical axis azimuth angle α.

4. The temperature measurement method according to claim 1 or 2, characterized in that, The DC amplitude V DC First harmonic amplitude V f Second harmonic amplitude V 2f They are respectively: V 1f =I0|r ss |K 1f 2J1(δ)sin2αε k (T) V 2f =I0|r ss |K 2f 2J2(δ)sin 2δ k (T) Among them, K DC K 1f and K 2f These are the amplification factors of the photodetector at DC, first harmonic, and second harmonic frequencies, respectively; J i (δ) is the Bessel function of cosδ and sinδ at the i-th harmonic, where i takes values ​​of 0, 1, 2, and δ is the periodic delay generated by the photoelastic modulator; θ k ε k Let represent the real part of the magneto-optical Kerr angle, the Kerr rotation angle, and the imaginary part, the ellipticity, respectively; I0 is the original intensity of the incident light; r ss This represents the Jones matrix coefficients of the sample.

5. The temperature measurement method according to claim 4, characterized in that, The magneto-optical signal MO(T) is: Among them, MO f (T) represents the amplitude of the first harmonic V. f With the DC amplitude V DC The ratio of MO; 2f (T) represents the amplitude of the second harmonic V. 2f With the DC amplitude V DC The ratio of .

6. The temperature measurement method according to claim 1, characterized in that, When the optical axis azimuth angles of the polarizer and the photoelastic modulator are adjusted to 90° and 0° respectively, the detection light intensity of the photodetector has only a DC component.

7. The temperature measurement method according to claim 1, characterized in that, Also includes: S5. Based on the numerical relationship between the magneto-optical signal MO(T) calibrated in S4 and the temperature T, calculate the actual temperature corresponding to the currently measured magneto-optical signal using a fitting method or a table lookup method.

8. A temperature measuring device based on a photoelastic modulation magneto-optical Kerr optical system, characterized in that, For performing the temperature measurement method according to any one of claims 1-7, the temperature measuring device comprises: The optimization configuration module is used to adjust the optical axis azimuth angle of the polarizer and the photoelastic modulator so that the detection light intensity of the photodetector has only a DC component; and to set the optical axis azimuth angle α of the analyzer to be less than 45°, and at the azimuth angle α, the detection light intensity is greater than the quantization error of data acquisition; The harmonic amplitude calculation module is used to obtain the DC amplitude, first harmonic amplitude, and second harmonic amplitude of the light intensity at the photoelastic modulation frequency by Fourier transform based on the detected light intensity. A magneto-optical signal calculation module is used to calculate the magneto-optical signal MO(T) of the magnetic nanofilm sample, wherein the magneto-optical signal MO(T) is the ratio of the first harmonic amplitude and the second harmonic amplitude to the DC amplitude, respectively; The temperature calibration module is used to change the temperature of the magnetic nanofilm sample and calibrate the numerical relationship between the magneto-optical signal MO(T) and the temperature T.

9. The temperature measuring device according to claim 8, characterized in that, The modulation frequency of the photoelastic modulator is not less than 50 kHz.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the temperature measurement method as described in any one of claims 1-7.

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